Development inhibitor releasing compounds or couplers (DIR's) are compounds that release development inhibitor compounds upon reaction with oxidized developer. DIR's are used in photographic materials to improve image sharpness (acutance), reduce gamma-normalized granularity (a measure of signal to noise ratio with a low gamma-normalized granularity indicating a beneficial high signal to noise ratio), control tone scale, and control color correction.
It is often desirable to maximize the amount of sharpness obtained from a DIR that is incorporated in a photographic element. One way this is accomplished is by increasing the mobility of the DIR without significantly increasing the quantity incorporated. This can be accomplished through the use of a timing group, which cleaves from the inhibitor only after a delay, during which the timing-inhibitor moiety can move in the material. An example of such a timed DIR is: ##STR1##
Another timed DIR, as taught in U.S. Pat. No. 4,409,323, releases a timing group from the DIR inhibitor fragment some time after the fragment is cleaved from the coupler by undergoing electron transfer along a conjugated system. These DIR's, however, do not provide reductions in gamma-normalized granularity to the extent that is often desirable.
It would therefore be highly desirable to provide a photographic material that offered the concommitant advantages of high image sharpness, low interlayer interimage effect, and low gamma-normalized granularity.
In an unrelated area, it has been taught to incorporate bleach accelerator-releasing compounds (BARC's) in photographic materials to aid in the bleaching step of photographic processing. European Patent Application Publication No. 193,389 discloses BARC's having a releasable thioether bonded to an alkylene group or heterocyclic nucleus with a solubilizing group attached thereto. One such BARC, having the formula: ##STR2## has been used as such in a color negative film, which also contained the above-identified DIR, D-1, which does not cleave the timing group from the inhibitor fragment by electron transfer along a conjugated system. This combination, as shown below by comparative data, did not provide as great a reduction in gamma-normalized granularity (from that provided by the DIR alone) as might be desired.
It has now been found that a specific subset of a class of compounds previously believed to be useful only as BARC's, allows for greater amounts of DIR's while maintaining the degree of color correction, and can provide the advantages of low interlayer interimage effect, high image sharpness, and low gamma-normalized granularity when used in combination with the above-described ballasted inhibitor-releasing compounds.